Rio Grande: Agate & Chalcedony Rockhounding in Starr County, Texas

Updated June 2026

Rio Grande is a mapped rockhounding spot in Starr County, Texas. Reported finds include agate, chalcedony, jasper. Below: coordinates, access notes, nearby spots, and trip-planning links.

Quick details

Access: Public area
County: Starr County
State: Texas
Coordinates: 26.36239, -98.83520

Geology at Rio Grande

This spot sits on ground mapped as Rio Grande River. Tough silica like agate and jasper typically survives weathering and collects as float in drainages and gravel.

Mapped unit: Rio Grande River
Elevation: 150 ft

Geologic mapping via Macrostrat and the underlying state geological survey maps (CC BY 4.0). Bedrock at the surface can vary within a mapped unit.

Best time to visit Rio Grande

Best months: October to April. Typical highs run 99°F in midsummer and 71°F in midwinter, with winter lows near 45°F. Summer heat here is intense, so carry more water than you think you need and work the early morning.

Climate normals: NOAA 1991-2020 monthlies, RIO GRANDE CITY station (2 mi away).

Land & collecting status

Generally open to casual rockhounding

Most public-tagged spots sit on BLM, U.S. Forest Service, or other federal land where reasonable hand collecting of common rocks and minerals is allowed. Confirm posted rules and active mining claims before you dig.

Public-land rules vary by agency, season, and field office. The RockHoundR app pulls live BLM, USFS, NPS, and tribal overlays so you can see exactly which agency manages the ground at this spot.

Sources & verification

Spot details combine the public RockHoundR location dataset, normalized mineral labels, agency land-status checks in the app, and community submissions. Coordinates are approximate until verified in the field.

State guidance last verified: April 1, 2026

Texas Parks and Wildlife Department
Bureau of Economic Geology — Texas geology
Big Bend National Park — Rules
Community submissions reviewed against published agency rules

Found at Rio Grande

Each chip opens all spots that produce that material; the encyclopedia link opens the full ID and field guide.

Nearby rockhounding spots

Other rockhounding spots within driving distance of Rio Grande.

Rio Grande FAQ

Where is Rio Grande?+

Rio Grande is in Starr County, Texas, at 26.36239, -98.83520.

What rocks and minerals can you find at Rio Grande?+

Rio Grande is reported to produce Agate, Chalcedony, Jasper.

Is collecting allowed at Rio Grande?+

Generally open to casual rockhounding. Most public-tagged spots sit on BLM, U.S. Forest Service, or other federal land where reasonable hand collecting of common rocks and minerals is allowed. Confirm posted rules and active mining claims before you dig. Always confirm current rules with the managing agency before a trip.

What tools should I bring to Rio Grande?+

Most agate and jasper is surface float: bring a spray bottle, a pick or small shovel, and a sturdy bag. Wet stones show their banding and translucence.

When is the best time to visit Rio Grande?+

The most comfortable months at Rio Grande are October to April. Summer heat here is intense, so carry more water than you think you need and work the early morning.

How do I get to Rio Grande?+

Open the directions link to navigate to 26.36239, -98.83520 in Google Maps. Some spots are remote, so check road conditions before driving out.

More rockhounding in Texas

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Open Rio Grande on the map

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